Part-time work: what is left net? (Excel)

What does this tool do?

Who is it for?

• Employees considering going 4/5 or half-time who want to know what that means net.
• Young parents weighing the cost of childcare against one day less at work.
• Anyone considering time credit, parental leave or an end-of-career job who wants to see the salary difference first.
• Couples working out which of them should reduce their hours, with the smallest loss of household income.

What is included?

• Input sheet with your full-time gross salary, the desired working regime and adjustable percentages for social security and withholding tax.
• Table with gross salary, social security contribution, taxable salary, withholding tax and indicative net at 100, 90, 80, 60 and 50%.
• Difference compared with full-time per month, per year and in percent.
• Line for double holiday pay and the end-of-year bonus in proportion to the working regime.
• Lines for costs that disappear (childcare, commuting, meals) and for an optional interruption allowance you enter yourself.
• A note on every assumption, so you know which figure to check on your payslip.

How do you use the file?

1. 1

   Open the file and go to the “Input” sheet. Only the yellow cells are meant to be filled in.

2. 2

   Enter your current gross monthly salary as it appears at the top of your payslip, without holiday pay or the end-of-year bonus.

3. 3

   Check the employee social security contribution. The default is 13.07%; leave it unless you work under a special status.

4. 4

   Adjust the withholding tax: take the amount from your current payslip and divide it by your taxable salary to know your real percentage. For the part-time regimes you can set a lower percentage, because a lower salary falls into lower tax brackets.

5. 5

   Enter the costs that disappear when you work less, for example one day of childcare per week or fewer commuting kilometres. Optionally enter the interruption allowance you would receive from the RVA/ONEM.

6. 6

   Look at the “Overview” sheet: it shows the indicative net salary per regime, the difference per month and per year and the effect on holiday pay and the end-of-year bonus. Change the regime to compare scenarios.

Worked example

A white-collar employee with a full-time gross salary of €3,500 goes 4/5. The social security contribution is 13.07%; the withholding tax is an assumption of 24% of taxable salary at full-time and 18% at 4/5, to illustrate progressivity. These are indicative figures, not a payroll calculation.

Gross falls by 20%, the indicative net by 13.7%. If €120 per month of childcare and commuting costs also disappear, the real difference becomes €196.43 per month. Double holiday pay and the end-of-year bonus do fall in proportion to salary, so by 20%.

Sources & calculation method

This is how the calculation is built:

1. Gross salary per regime = full-time gross × percentage (100, 90, 80, 60 or 50%). That is proportional; a 4/5 regime gives 80% of the full-time gross.
2. Employee social security contribution = gross salary × 13.07%. Taxable salary is gross minus that contribution. Reductions such as the work bonus for low salaries are not in the model.
3. Withholding tax = taxable salary × the percentage you set per regime. The model deliberately uses an effective percentage instead of the official scales; those depend on your family situation and change every year.
4. Indicative net salary = taxable salary − withholding tax. Difference per month = net full-time − net part-time; per year = difference × 12. Disappearing costs and an optional interruption allowance are deducted from that difference.
5. Double holiday pay and the end-of-year bonus are calculated proportionally: full-time amount × working regime. The file does not convert them to net.

Assumptions

• The employee social security contribution of 13.07% applies to private-sector employees: 7.50% pensions, 3.55% healthcare, 1.15% sickness and disability benefits and 0.87% unemployment, according to the administrative instructions of the RSZ/ONSS.
• Withholding tax is an assumption you enter yourself. The real amount depends on your family situation, dependent children and the scales of the year; the final tax follows through your personal income tax return.
• Holiday pay and the end-of-year bonus are calculated proportionally. Some sectors apply other rules, for example blue-collar workers who receive their holiday pay through the RJV/ONVA.
• The model assumes a single gross salary, without meal vouchers, benefits in kind or bonuses. You can include those separately in the household budget.

Limitations

• The file is not a payroll calculation and does not replace a simulation by your employer or payroll provider.
• It does not calculate the RVA/ONEM interruption allowance for time credit or thematic leave; you enter that amount yourself.
• The effect on your pension build-up is not quantified; some forms of time credit are assimilated, plain part-time work is not.

Sources

This page and the file were last updated on September 24, 2026. Legislation and rates may have changed since.

Frequently asked questions